The ACS™ (Asherman Chest Seal) is a sterile occlusive dressing for treating open pneumothorax and preventing tension pneumothorax in chest injuries from gunshots, stab wounds, or other penetrating chest trauma. The unique one-way valve is designed to let air and blood escape while preventing re-entry of either. Proven to be more effective treatment than standard petroleum gauze, the ACS is standard issue for the US Army, the British Army and the US Navy. The ACS is 5.5" in diameter, includes a gauze pad (4" x 4") to clean and dry the wound, and is clear so the wound can be observed.